As a result of handling errors during assembly, electromagnetic relays, electromechanical modules and devices can fall onto the ground and therefore need to be drop-resistant, i.e. they must endure the impact resulting from being dropped from a specified height of, for example, 1 or 2 meters without suffering any internal damage or functional limitation. In order to prevent a component which looks undamaged on the outside from proving to be inoperable on account of such damage after fitting, it is necessary either for the device to endure free fall from a defined height without suffering any prior damage, or for the damage to be visible on the outside as well.
Housings for relays, modules and devices are usually designed to be planar over a large area on the outside to allow the use of as large an interior as possible, and have ribs and projections in the interior in order to secure the component against impact and shock stress. As the impact absorption of plastic housings is very small, the latter also having to ensure mechanical protection of the components and therefore being made of a high-strength plastic, the component in the housing requires a relatively large additional expense in terms of design so that it will survive a drop test without suffering any hidden damage. This large additional expense is required only for the infrequently occurring situation in which the component is dropped owing to a handling error before it is actually used. When the specifically, when component is in normal use, such impact stresses will not occur throughout its entire life.